The Amazon soil, normally red, is scattered with dark patches. These are charcoal residues from human occupation, some of them thousands of years old. Elemental particulate carbon is a good cation exchange medium - it sequesters nutrients - and it makes these patches extremely fertile when compared to untouched soil.

A good plan might be to is to char biomass and simply plough it into soil, if carbon sequestration is what you are about. This can eb combined with conventional agriculture. (NB by the way, that a field covered in soya or sugar cane exchanges as much carbon as a tropical rain forest: it's just and energy-in energy-out issue. Standing tropical forest holds about twice as much carbon as uncharred sugar cane, but less if the residue bagasse were to be charred and storred.) The issue with forests is biodiversity, not net photosynthesis.

Consider another practical CO2 sequestration project. Provide the simple, locally-sourced technology and then pay India small holders to set up cheap windmills, not for power but to grind chunks of the immense Deccan Flats to a powder. Why? Because these hundreds of cubic kilometres of rock are made of a basic basalt, one that rapidly absorbs CO2 when it is ground up and so exposed to air. What you get from the residue are new rice paddies.

It is thought that the reason that the climate got cold after the 15C-hotter-than-now Eocene is that the newly-forming Himalayas began to erode, fixing CO2 as they did so. The resulting carbonates are under Bangaldesh and in the Bay of Bengal.

Another good scheme is to use biomass-based carbon as a spine on which to hang solar (etc) derived hydrogen. The result is called diesel or gasoline. Doing this uses 1950s technology, and is a lot cheaper than many alternatives. You can of course burn it in cars, using established technology and known, safe handling systems. You have tens of millions of trained technicians already on stream. Hydrogen is, by contrast, a nightmare fuel: low energy density, hard to store and with a tendency to embrittle anything in which it is stored, essentially explosive in any contact with the atmosphere. And as to electricity! Has anyone seen a Lithium battery on fire? Think disruptive crash - fizz, crackle, boof.

0: We are wrong about the life: it does take the finger of a deity.

1: They have better communications media that we cannot access.

2: It's dangerous out there: croaking frogs attract snakes.

3: We are in a game park: they communicate with us only when we have something to offer.

4: All technological civilisations always try one key experiment that sinks the ship: e.g. massive self-gravitating Bose-Einstein condensate >> black hole >> zip.

5: Singularity: biochemical 2 eV life is just too limiting and civilisations move on when they can. "On" may be into simulations, or into media that e don't know about.

Notes:

On 3 - self-propagating von Neumann machines can (theoretically) cover the galaxy in a few million years. Dust like seeds, working up to "plants" in the Oort, spraying their kind onwards in an endless chain. If symbol-using life is found, infest its nervous system and nroadcast on ege dark matter wavebands (? :) ) you you and I are either databased - immortality of a sort - or appearing on Arcturan TV.

On 4: Add themes to taste; or just accept that a critical mass of capability means that someone, somewhere always does it on purpose. 60+% of traffic head on collisions are "taking the bastards with me."

On 5: If we can understand congition as a physical process then we can emulate it as one. There is probably no difference between the quality of being aware that you have, that I have or that the steak that you had for dinner possessed when it wandered about and mooed. What differs is sensorium, memories, affect/ reflex balances.

What individuates You from Moo is probably a few GB, so the delta from standard human awareness that is You could fit on a DVD. Basic human awareness OS is - let's say - 1 TB, "you" 1-5 GB on top of that. So really not a very difficult task to emulate once you understand the basics; which we do not at all understand now, but which we will in 30-40 years.

Reading out "you" from the wetware is probably not a bit by bit fiddle but 'just' sensing statistically the balance between generic pay offs and balances in your processing characteristics. For example, a tree, as perceived by you now, or recalled later, is represented from a hardwired GL, tweaked to reflect as much detail as is required for the observation. Recalling that 'there were some trees' generates a vague and very geenral set of blobs in one's mind, after all. Memories of a tree or a face are essentially tweaked primitives: from generic face to 'Her' face 'Then' calls up some standard ways in which faces differ and a lot of links to other generics, themselves forming a web of what feel like memories.

So: backups, hacks, file transfers, upgrades, edits. Add better hardware. Massively parallel games for real - science fiction has been there already. Be Your Own Universal Emperor For Fake Real, or suffer arthritis and mortgage worries whilst trying to telephone Arcturus for Real real - which would you prefer?

In the Economic Geography of Talent (Carnegie Mellon 2005), Richard Florida looked at what made capable people come to work in technology-using clusters. The study – which mixed focus groups with statistical surveys – started from the hypothesis that what would bring talent together was a mixture of economic opportunity, diversity and amenity, including climate, housing costs and the like. The conclusion was that talent was intensely concentrated geographically; that the single greatest attractor to talent was the presence of other talent; and that high technology industries attracted talented people, who in turn drew in more of their fellows, which in turn created more high technology industry. Regional income levels were important, but probably a consequence rather than a cause of talent clusters. Social factors had some impact on this. Specifically, tolerance for diverse life styles was significant, with the density of gay-related facilities proving particularly important to the statistics and interviews. (See www.chforum.org/scenarios2009/agents.shtml for more.) One additional factor is this. Above average income in technology clusters tend to be earned by non-technologists. Those with technical qualifications earn below the regional median for professionals. The chief reason seems to be associated witht he ability to manage human networks. Technologists tend to be introverted, score highly on schizoid and neuroticism scales. That is, they are bad at handling the huge complexity of human interaction, the heart and soul of management. What is the relevance of that? Well, local networks take a while to create, so people who live through them are pinned to that locale. People who are essentially unconnected to their local society can easily move. Sad, but...

Metal air batteries - like Lithium, but also Aluminium and Magnesium, for example - offer a proven technology for storing energy. Many renewables are intermittent, or located in places without energy demand. Take a wind turbine. You can connect it to the grid with a (usually verty expensive) line and manage its variable productivity, or you can hitch it to a bucket of electrolyte, and occasionally harvest a billet of metal.. Ocean thermal is one of the few renewable technologies that is both reliable and ona scale that matches real world energy demand. However, hot water over a thermocline is chiefly found near the equator, where energy demand is, on the whole, low. So smelt to metals in situ, move these (safely, in a non-toxic form) to the industrial centres, "burn" it to oxide and generate electricity. Now collect the oxide, send it back and re-smelt it. This is a carbon-free technology (Aluminium is approaching zero carbon with direct reduction crucibles) and it is safe, proven and ready for the oven. BTW, if Lithium takes off, buy shares in Bolivia, which has a huge fraction of proven reserves.

Perhaps you can help me on this. I read the paper, and absorbed most of what he had to say. The style is very clear. If only others in arxiv would follow... What I did not get was how distance is created. Time is taken care of with a Killing vector,which amounts to saying that "time is". But distance is supposed to be emergent. The discussion on 'foliation' might cover this, but if so I did not get it. If diffusion - as you term it - is to happen, then there needs to be some form of cardinality. That is, if there are three 'masses-behind-a-screen', A, B and C, then if A is to diffuse to C, it needs to know that B is in the way; or that B is "closer" than C. Second, if screens are essentially arbitrary - any collection of mass has a screen, and thus all configurations of all the mass there is can bs (are, in the theory) assigned to arbitrary sets, each with a screen - then does one not rapidly run into infinities and worse, combinatorial infinities, if the cardinality issue is not somehow settled?